[SOLVED ] -- Linux Ubuntu Xenial - kernel panic - not syncing : VFS : Unable to mount root fs

#Seen below , ID for recent Kernel = 4.4.0-164-generic , which is the Kernel which was being auto-updated by the GUI , its labeled as NOT TAINTED , this i need to check further - whats with the NOT TAINTED ? 
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 kernel panic - not syncing : VFS : Unable to mount root fs on unknown-block(0,0)
CPU: 1 PID : 1 Comm: swapper/0 not tainted 4.4.0-164-generic #192-Ubuntu
Hardware name : Apple Inc. MacbookPro5.5/Mac-F2268ACB , BIOS MBP55.88Z.00AC.B03.0906151708 06/15/09

Call Trace :
dump_stack*0x63/0x82
panic+0xd3/ 

Solved by hard shutdown , again started and got into the GNU GRUB menu - the screen with the prompt == grub> 
This was the wrong place to be - thus == grub> normal ... and yes now back to the GRUB MENU.
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Here  2 Kernels listed - 1/  4.4.0-164-generic , with (upstart) and (recovery mode),     2/ 4.4.0-31-generic , with (upstart) and (recovery mode)

Went ahead and chose -
4.4.0-31-generic , did not use a live disc or usb to boot back in , as of now all systems - Go !! lets see what else is required ...


#Further reading ....
SPECIAL CASE --- User Created OWN CUSTOM KERNEL --- https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1653636